The invention relates generally to apparatus for substrate processing and, more particularly, to integration of a compact, self-contained remote plasma generator with a substrate processing system.
The fabrication of semiconductor products, such as integrated circuits, often involves the formation of layers on a substrate, such as a silicon wafer. Various techniques have been developed for the deposition processes, as the layers often involve different materials. For example, a metal layer might be deposited and patterned to form conductive interconnects, or a dielectric layer might be formed to electrically insulate one conductive layer from another. Some types of layer formation processes that have been used to form layers of dielectric materials and other materials are chemical vapor deposition (CVD) processes.
CVD processes include the deposition processes, in which precursor gases or vapors react in response to the heated surface of the substrate, as well as plasma-enhanced CVD (xe2x80x9cPECVDxe2x80x9d) processes, in which electro-magnetic energy is applied to at least one precursor gas or vapor to transform the precursor into a more reactive plasma. Forming a plasma can lower the temperature required to form a film, increase the rate of formation, or both. Therefore, plasma enhanced process are desirable in many applications.
When a layer is formed on a substrate, some material is usually also deposited on the walls of the deposition chamber and other components of the deposition system as residue. The material on the walls of the chamber is generally undesirable because the residue can build up and become a source of particulate contamination, causing wafers to be rejected. Several cleaning procedures have been developed to remove residue from inside the chamber. One type of procedure, known as a xe2x80x9cwet-cleanxe2x80x9d is performed by partially disassembling the deposition chamber and wiping the surfaces down with appropriate cleaning fluids. Other types of cleaning processes utilize a plasma to remove the residue by converting it to a volatile product that can be removed by the chamber exhaust system. These processes are known as xe2x80x9cdryxe2x80x9d cleans.
There are two general types of plasma dry cleaning processes. One type forms a plasma inside the processing chamber, or xe2x80x9cin situxe2x80x9d. An example of an in situ plasma clean uses NF3 and C2F6 gases to form free fluorine for removing residue in the chamber interior. The other type forms a plasma in a remote plasma generator and then flows the ions into the processing chamber. Such a remote plasma cleaning process offers several advantages, such as providing a dry clean capability to a deposition system that does not have an in situ plasma system. Furthermore, a remote plasma system might be more efficient at converting cleaning plasma precursor gases or vapors into a plasma, and forming the plasma outside the chamber protects the interior of the chamber from potentially undesirable by-products of the plasma formation process, such as plasma heating and sputtering effects. The use of a remote plasma system also reduces perfluorocarbon (PFC) emissions. On the other hand, remote plasma systems suitable for CVD systems are typically expensive and bulky, and may be impractical or economically unfeasible. Retrofitting existing CVD systems with a remote plasma generator may require substantial alterations that are costly and time-consuming.
The present invention is directed toward the integration of a compact, self-contained, low-cost remote plasma generator with a substrate processing apparatus. In specific embodiments, the remote plasma generator is mounted to the lid of a process chamber above the substrate holder disposed therein. A gas delivery system is provided to direct a cleaning plasma precursor through the remote plasma generator to the process charmer for generating cleaning plasma species to clean the chamber in a clean operation. During deposition, the gas delivery system directs one or more process gases into the process chamber while bypassing the remote plasma generator. A mixing device provides a short, direct flow path for the cleaning plasma species from the remote plasma generator to the process chamber during the clean operation, and long mixing paths for mixing a plurality of process gases during the deposition process. The integration requires only minor alterations to existing process chambers, and is particularly suitable for retrofitting such chambers at a low cost with minimal system downtime. The integration is sufficiently robust to be adaptable to different chamber configurations. In addition to significantly reducing PFC emissions, the integrated system increases throughput by reducing clean times, thereby lowering operating cost. The integrated system may also extend the life of 1he CVD system by eliminating harmful effects to the chamber interior caused by in situ plasma cleaning processes.
In accordance with an aspect of the preset invention, a substrate processing system includes a housing defining a process chamber, and a substrate support for supporting a substrate during substrate processing in the process chamber. The system further includes a remote plasma generator having au inlet and an outlet, and a gas delivery system for introducing gases into the process chamber. The gas delivery system includes a three-way valve having a valve inlet, a fist valve outlet and a second valve outlet. The three-way valve is adjustable to switch flow between a first valve path from the valve inlet to the first valve outlet and a second valve path from the valve inlet to the second valve outlet. A first inlet flow conduit is coupled between the outlet of the remote plasma generator and the process chamber. A remote plasma conduit is coupled between the first valve outlet of the three-way valve and the inlet of the remote plasma generator. A second inlet flow conduit is coupled between the second valve outlet of the three-way valve and the process chamber.
In some embodiments, the gas delivery system includes a third inlet flow conduit coupled with the process chamber. The gas delivery system includes a mixing block having a first flow path for directing gas flow from the remote plasma generator through the first inlet flow conduit to the chamber. The mixing block includes a second flow path coupled between the second inlet flow conduit and the process chamber, and a third flow path coupled between the third inlet flow conduit and the process chamber. The second and third flow paths in the mixing block are at least partially overlapped and include multiple turns to induce mixing of process gases from the second and third inlet flow conduits.
In a preferred embodiment, the remote plasma generator is mounted on the lid of the housing disposed generally above the substrate support in the chamber. A ceramic isolator is coupled between the remote plasma generator and the process chamber, and includes a flow passage to facilitate gas flow between the remote plasma generator and the process chamber. During an in situ plasma process in the chamber, the process gas may backstream toward the remote plasma generator. The presence of the process gas between the RF hot components of the chamber on one side and the grounded mounting hardware for mounting the remote plasma generator to the chamber on the other side may induce formation of a secondary plasma in that region. The secondary plasma may cause instability of the plasma inside the chamber and adversely affect the deposition. The ceramic isolator isolates the RF hot components of the chamber from the grounded mounting hardware to avoid formation of a secondary plasma
In accordance with yet another aspect of the invention, a substrate processing system includes a housing defining a process chamber, a substrate support for supporting a substrate during substrate processing in the process chamber, and a remote plasma generator. The system further includes a first gas line, a second gas line, a first gas supply for a first gas, a second gas supply for a second gas, and a third gas supply for a third gas. A device is provided for coupling the first gas supply with the first gas line to flow the first gas through the first gas line and the remote plasma generator to the process chamber during a first operation. During a second operation, the device couples the second gas supply with the first gas line to flow the second gas trough the first gas line to the process chamber bypassing the remote plasma generator, couples the third gas supply with the second gas line to flow the third gas into the process chamber, and mixes the second gas and the third gas together prior to flowing the second and third gases into the process chamber.